Relatively small, self contained, modular waste water treatment devices have been used in the marine industry to avoid discharge at sea of contaminated waste waters and to eliminate the need to store waste waters on board. Such prior art waste water treatment devices meet the Coast Guard standards for overflow discharge of treated effluent. One requirement for marine waste water treatment units is that they should be small enough to be moved easily through vessel doors and to occupy a minimum amount of vessel space. The unit also should have the capability, via modular constitution, of being installed at sea to avoid costly vessel tie up time.
A typical marine industry waste water treatment device presently used is described in U.S. Pat. No. 3,638,590. In accordance with such typical prior art devices, the waste water is collected in a first vessel for separation of non-colloidal solid wastes and the separated solid wastes are comminuted to a maximum particle size of about 1/4 inch. The waste water, including the comminuted solid wastes then are tranferred to a second vessel for coagulation by contact with a suitable high molecular weight polyelectrolyte and the coagulated solid wastes are removed from the liquid wastes in a separate device, such as a centrifuge. The liquid wastes then are directed to a third vessel for disinfection by contact with a suitable chemical, such as sodium hypochlorite. The disinfected liquid wastes may be further purified by absorption of the dissolved organics in a fourth vessel by contact with a suitable absorbant, such as activated charcoal. Other, similar marine sanitation units have been developed which utilize the above-described process steps without the need for solids comminution. One such unit is the SANI-SYSTEM 600 TYPE I device manufactured by CLEAR WATER, INC. Subsidiary of La Mere Industries, Inc., Walworth, Wisconsin, described in Form No. 597169-77.
In each of these prior art sanitation units it has been necessary to use separate vessels for the ordered process steps of solids coagulation, separation, and disinfection. In accordance with the present invention, it has been found that these three process steps can be carried out effectively in a single treatment vessel of particular construction by contacting the waste water with coagulant and disinfectant on route to the treatment vessel.